查看更多>>摘要：Silicon waveguides typically exhibit optical anisotropy,which leads to polarization correlation and single-polarization operations.This consequently creates a demand for polarization-control devices.This paper introduces a CMOS-compatible 0-band reconfigurable TE/TM polarization rotator comprising two symmetrical polarization rotator-splitters and phase shifters.This configuration enables dynamic conversion of any linear polarization to its quadratic equivalent.Experimental results indicate that the reconfigurable polarization rotator exhibits an insertion loss of less than 1.5 dB.Furthermore,the bandwidth for a polarization extinction ratio beyond 15 dB exceeds 60 nm.
查看更多>>摘要：The dual-mode stabilization scheme has been demonstrated as an efficient way to stabilize laser frequency.In this study,we propose a novel dual-mode stabilization scheme that employs a sizable Fabry-Pérot cavity instead of the microcavity used in previous studies and has enabled higher bandwidth for locking.The results demonstrate a 30-fold reduction in laser frequency drift,with frequency instability below 169 kHz for integration time exceeding 1 h and a minimum value of 33.8 kHz at 54 min.Further improvement could be achieved by optimizing the phase locking.This scheme has potential for use in precision spectroscopic measurement.
查看更多>>摘要：We present a study on a watt-level acousto-optically Q-switched Pr∶YLF laser at three different repetition rates[10 kHz,20 kHz,and 50 kHz]for the first time,to the best of our knowledge.The corresponding average output powers and pulse widths were measured to be 1.14 W,1.2 W,and 1.32 W,and 40 ns,52 ns,and 80 ns,respectively.A maximum pulse energy of 0.11 mJ was obtained,corresponding to a peak power of up to 2.8 kW at a repetition rate of 10 kHz.The simulated dynamics of a fast Q-switched Pr∶YLF laser is in agreement with the experiment.The laser's ability to generate stable pulses with high peak power and short pulse width makes it highly desirable for various practical applications,such as laser machining and material processing.
查看更多>>摘要：We present our efforts towards power scaling of Er∶Lu203 lasers at 2.85 μm.By applying a dual-end diode-pumped resonator scheme,we achieve an output power of 14.1 W at an absorbed pump power of 59.7 W with a slope efficiency of 26％.In a single-end pumped resonator scheme,an output power of 10.1 W is reached under 41.9 W of absorbed pump power.To the best of our knowledge,this is the first single crystalline mid-infrared rare-earth-based solid-state laser with an output power exceeding 10 W at room temperature.
查看更多>>摘要：Toroidal multipole is a special current distribution that has many different characteristics from electric multipole and mag-netic multipole distributions.Because of its special properties,the toroidal dipole is a research hotspot in the field of metamaterials and nanophotonics.However,the low scattering of the toroidal dipole moment makes its excitation a chal-lenging task.At present,there are relatively few studies on its specific engineering applications.In this paper,by slotting in the rectangular cavity,the excitation of an equivalent toroidal dipole is successfully achieved over a wide frequency range of 53-58 GHz.Results indicate that under the action of the toroidal dipole,the TE10 mode electromagnetic waves transmitted in the rectangular waveguide are converted into vector beams and are radiated outwards.Further adjusting the spatial distribution of the magnetic dipoles in the toroidal dipoles yields results that indicate that the resonance mode in the slot is still dominated by the magnetic toroidal dipole moment,and the electromagnetic waves radiating outward are vortex beams carrying vector polarization.The scattered energy of each dipole moment inside the antenna is calculated.This calculation verifies that the mass of the vector beam and vector vortex beam is closely related to the toroidal dipole supported by this antenna.The proposed structure can be applied to explorations in vortex filtering,in photon entanglement,and in the photonic spin Hall effect.
查看更多>>摘要：We propose a laser speckle contrast imaging method based on uniting spatiotemporal Fourier transform.First,the raw speckle images are entirely transformed to the spatiotemporal frequency domain with a three-dimensional(3D]fast Fourier transform.Second,the dynamic and static speckle components are extracted by applying 3D low-pass and high-pass filter-ing in the spatiotemporal frequency domain and inverse 3D Fourier transform.Third,we calculate the time-averaged modu-lation depth with the average of both components to map the two-dimensional blood flow distribution.The experiments demonstrate that the proposed method could effectively improve computational efficiency and imaging quality.
查看更多>>摘要：We propose a spatially chirped quasi-phase-matching[QPM]scheme that enables ultrabroadband second-harmonic-gen-eration[SHG]by using a fan-out QPM grating to frequency-convert a spatially chirped fundamental wave.A"zero-dispersion"4f system maps the spectral contents of ultrabroadband fundamental onto different spatial coordinates in the Fourier plane,where the fundamental is quasi-monochromatic locally in picosecond duration,fundamentally canceling high-order phase mismatch.A fan-out QPM grating characterized by a linear variation of the poling period along the trans-verse direction exactly supports the QPM of the spatially chirped beam.We theoretically demonstrate the SHG of an 810-nm,12.1-fs pulse into a 405-nm,10.2-fs pulse with a conversion efficiency of 77％.
查看更多>>摘要：Radio frequency/microwave-directed energy sources using wide bandgap SiC photoconductive semiconductors have attracted much attention due to their unique advantages of high-power output and multi-parameter adjustable ability.Over the past several years,benefitting from the sustainable innovations in laser technology and the significant progress in materials technology,megawatt-class output power electrical pulses with a flexible frequency in the P and L microwave wavebands have been achieved by photoconductive semiconductor devices.Here,we mainly summarize and review the recent progress of the high-power photonic microwave generation based on the SiC photoconductive semiconductor devi-ces in the linear modulation mode,including the mechanism,system architecture,critical technology,and experimental demonstration of the proposed high-power photonic microwave sources.The outlooks and challenges for the future of multi-channel power synthesis development of higher power photonic microwave using wide bandgap photoconductors are also discussed.
查看更多>>摘要：In this paper,we demonstrate nBn InAs/InAsSb type Ⅱ superlattice[T2SL]photodetectors with AlAsSb as the barrier that targets mid-wavelength infrared[MWIR]detection.To improve operating temperature and suppress dark current,a specific Sb soaking technique was employed to improve the interface abruptness of the superlattice with device passivation using a Si02 layer.These result in ultralow dark current density of 6.28 × 10-6A/cm2 and 0.31 A/cm2 under-600 mV at 97 K and 297 K,respectively,which is lower than most reported InAs/InAsSb-based MWIR photodetectors.Corresponding resistance area product values of 3.20 × 104 Ω·cm2 and 1.32 Ω·cm2 were obtained at 97 K and 297 K.A peak responsivity of 0.39 A/W with a cutoff wavelength around 5.5 μm and a peak detectivity of 2.1 × 109 cm·Hz1/2/W were obtained at a high operating temperature up to 237 K.
查看更多>>摘要：The dynamics of water within a nanopool of a reverse micelle is heavily affected by the amphiphilic interface.In this work,the terahertz[THz]spectra of cyclohexane/lgepal/water nonionic reverse micelle mixture are measured by THz time-domain spectroscopy and analyzed with two Debye models and complex permittivity of background with volume ratios.Based on the fitted parameters of bulk and fast water,the molar concentration of all kinds of water molecules and hydration water molecule number per Igepal molecule are calculated.We find that slow hydration water has the highest proportion in water when the radius parameter ω0＜10,while bulk water becomes the main component when ω0 ≥ 10.The fea-ture radius ratio of nonhydrated and hydrated water to total water nanopool is roughly obtained from 0.39 to 0.85 with increasing ω0.
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